URHM38E – Tempest® Aviation Massive Electrode Spark Plug
Available now on the Airparts.aero Marketplace.
Overview
The Tempest® URHM38E is a high-performance, FAA-PMA certified massive electrode aviation spark plug, engineered for exceptional durability and reliability in a wide range of Lycoming and Continental piston engines. This is a flight-critical component that serves as the heart of the ignition system, responsible for delivering a powerful, high-energy spark to initiate combustion. The URHM38E is a traditional, robust "massive electrode" design, featuring large nickel alloy electrodes that provide an exceptionally long service life and are highly resistant to the harsh environment inside an engine's combustion chamber.
Every component of this spark plug is engineered to aerospace standards, from the high-purity alumina ceramic insulator to the proprietary "Hot-Lock" gas-tight seal. The "R" in the part number designates an integrated resistor, which is critical for suppressing radio-frequency interference (RFI) that can disrupt cockpit avionics and communication radios. As a proven, cost-effective, and highly reliable choice for thousands of general aviation aircraft, the Tempest URHM38E is the workhorse of piston engine ignition.
Key Features
FAA-PMA Certified: A fully certified, airworthy component, approved as a direct replacement for equivalent Champion and Autolite plugs.
Massive Nickel Alloy Electrodes: Features a robust, two-prong massive electrode design made from a high-performance nickel alloy, providing a long service life and excellent resistance to wear.
Integrated RFI Resistor: A built-in resistor virtually eliminates radio-frequency interference, protecting sensitive avionics and ensuring clear communications.
High-Purity Alumina Insulator: Utilizes a proprietary, high-purity aluminum oxide ceramic insulator for superior dielectric strength, thermal conductivity, and resistance to thermal shock.
Proprietary Nickel Finish: The steel shell is coated with a proprietary nickel finish for superior corrosion and rust protection compared to traditional zinc plating.
"Hot-Lock" Gas-Tight Seal: A proprietary conductive glass seal is fired in place, creating a monolithic, 100% gas-tight seal between the center electrode and the insulator, preventing combustion gas leakage.
Technical Specifications
Part Number: URHM38E
Component Type: Aviation Spark Plug
OEM Manufacturer: Tempest® Aero Group
Cross-Reference: Replaces Champion RHB38E, Autolite UREM38E.
Design: U (Tempest Design), R (Resistor), H (Long Reach), M (Massive Electrode)
Thread Size: 18mm
Thread Reach (-H): 3/4 inch
Hex Size: 7/8 inch
Electrode Material: Nickel Alloy
Aircraft Compatibility
The URHM38E is a standard spark plug for a vast range of the most popular piston engines in general aviation, including but not limited to:
Lycoming Engines: O-235, O-320, IO-320, O-360, IO-360, AEIO-360 series.
Continental Engines: O-200, O-300, GO-300 series.
Common Aircraft Applications: This encompasses a huge fleet of aircraft, including the Cessna 150/152/172, Piper PA-28 Cherokee/Warrior/Archer, Grumman AA-5 series, and many others.
Note: This is a flight-critical engine component. The specific engine Illustrated Parts Catalog (IPC) or maintenance manual is the final and absolute authority for determining part applicability.
Applications
Piston Engine Ignition: Delivers the high-voltage spark required to ignite the compressed fuel/air mixture in the combustion chamber.
General Aviation: The standard, reliable choice for training, personal, and utility aircraft.
Why Choose URHM38E?
The ignition system has zero redundancy; a reliable spark is non-negotiable. The Tempest URHM38E is a premium, FAA-PMA certified plug that often incorporates design improvements over the original parts. Tempest's proprietary features, such as the superior nickel plating and the advanced "Hot-Lock" center seal, are engineered to provide a more reliable, longer-lasting, and more corrosion-resistant plug. The massive electrode design is a proven, durable, and cost-effective solution for ensuring consistent ignition performance. For operators seeking a combination of proven reliability and modern manufacturing enhancements, the Tempest URHM38E is the professional's choice.
A critical engineering challenge in any spark plug's design is the center electrode seal. This seal must simultaneously perform three contradictory functions under extreme conditions: 1) It must be a perfect, hermetic seal to contain combustion pressures that can exceed 1,000 PSI. 2) It must be an excellent electrical conductor to transfer the magneto's high-voltage pulse to the electrode tip with minimal energy loss. 3) It must have a coefficient of thermal expansion that is precisely matched to both the steel center electrode and the surrounding alumina ceramic insulator to maintain the seal's integrity from a -40°F cold start to the 1,500°F+ temperatures of combustion. Tempest's proprietary "Hot-Lock" technology addresses this by using a specific formulation of conductive, vitrified glass powder. This powder is poured into the assembly and then melted in place, fusing the components together and creating a monolithic, gas-tight, conductive seal that is exceptionally resistant to thermal shock and mechanical vibration.
Note: The URHM38E is a flight-critical engine component. It must be installed by a certified A&P/IA mechanic. The electrode gap must be checked and set to the dimension specified in the engine manual. Use a new copper gasket and apply an aviation-grade, electrically conductive anti-seize compound to the threads of the plug only. Do not get anti-seize on the electrodes. The plug must be tightened to the specific torque value listed in the engine maintenance manual using a calibrated torque wrench and the correct deep socket.
Documentation
Tempest® Aero Group Website: Full application charts, cross-reference guides, and technical documents for the entire line of Tempest spark plugs are publicly available for download from the official Tempest website.
FAA-PMA Eligibility: [ Click Here ]
Product Overview:
Not your grandfather's spark plugs!
The best spark plugs at the best price
- 'Fired in' resistor for stable resistance value and smoother running engine
- Zero-leakage seal encloses hot, high pressure combustion gases
- Durable nickel finish offers wear and corrosion resistance
- Ceramic insulator provides high performance in severe operational conditions
- Reduced fouling and enhanced heat range control
- 1. High Conductivity Copper Core Center Electrode
Copper, co-extruded inside a nickel alloy sleeve ensures outstanding heat and electrical conductivity while the nickel sleeve offers high resistance to corrosive combustion gases. - 2. Proprietary Glass Center Seal
21st century “fired in” resistor replaces the multipart screw, spring, and carbon pile stack up used in competitive plugs and known to suffer from resistance value instability that can cause misfires, wasted fuel, and engine roughness. - 3. High Alumina Ceramic Insulator
High mechanical strength, superior dielectric properties, and proprietary protective glaze, provides high performance to conquer severe operational conditions. “Clean Collar” massive electrode “V” tip focuses heat to reduce fouling and enhance heat range control. - 4. Nickel Finish
Environmentally preferable electrolytic nickel provides outstanding durable finish, superior corrosion protection, and extreme wear resistance. - 5. Nickel Ground Electrodes
Aviation grade nickel electrode design focuses on minimizing sparking voltage requirements while maintaining specification gaps to ensure large, stable “flame kernels” for on-time ignition and complete combustion. - 6. Vacuum Infused Center Electrode
The proprietary vacuum infusion process seals the electrode/insulator gap providing stable heat range and superior center electrode cooling (heat flow to the insulator). - 7. Hot-Lock Assembly
Intense pressure and heat create positive, zero-leakage, shrunken in seal between insulator and shell to contain the hot, high pressure combustion cycle gases. - 8. Harness Wire Contact
The spring contact surface is smooth, uninterrupted, oxide-treated, and corrosion resistant. It’s chemically bonded to the fired-in resistor providing the ultimate harness/spark plug termination integrity and energy transfer.
URHM38E Spark plug specifications:
- • Reach ( 1/2" )
- • Connector Threads ( 5/8"-24 )
- • Electrode design ( Massive )
Tempest Spark Plug : Application Guide[ link ]